The police had requested air support after a Taliban attack near their outpost near the outskirts of Lashkar Gah, the capital of Helmand Province.

Attaullah Afghan, the head of Helmand’s provincial council, estimated the police death toll at 17, including a commander and his assistant, and said that 14 more people were wounded.

Col. Dave Butler, a spokesman for the American-led mission in Afghanistan, said that the Americans had coordinated with Afghan officials and had confirmed that the “areas were clear of friendly forces.”

“Unfortunately, they were not, and a tragic accident resulted,” Colonel Butler said in a statement. “Afghan Security Forces as well as Taliban fighters were killed in the strikes. We’re examining the miscommunication to ensure it is not repeated.”

The airstrike is the latest in a cluster of American friendly-fire incidents this year. Twice in March, American ground troops exchanged gunfire with friendly Afghan forces. Both attacks resulted in airstrikes that left more than a dozen people dead or wounded, including civilians.

At the time, American officials said the cases resulted from fighting in a “complex environment” and the “fog of war.”

The airstrike on Thursday was most likely a byproduct of not having American troops on the ground. Directing and approving airstrikes from miles away, as often happens across Afghanistan, can sometimes be prone to error.

In most cases, American troops are watching an array of video feeds from drones or other aircraft overhead, while others are also trying to communicate with those Afghans in the middle of the battle, sometimes using cellphones and speaking through interpreters, to ensure the aircraft has the right target.

A similar scenario played out in Helmand in July 2017, when an American airstrike killed 16 Afghan police officers in nearby Gereshk district.

Helmand Province is the Taliban’s heartland and the source of the group’s economic lifeline and main cash crop: poppy. In March, a small group of Taliban fighters, with the help of Afghan Army insiders, infiltrated Camp Shorab, one of the most vital bases in Helmand, before being repelled. The militant group currently controls much of the province.